Heat pump system



May 20, 1952 A. c. HOMEYER 2,597,729

HEAT PUMP SYSTEM Filed July 18, 1951 5 Sheets-Shea? l BY//Q M@ May 201952 A. c. HoMr-:YER 2,597,729

HEAT PUMP SYSTEM Filed July 18 1951 5 Sheets-Sheet 2 )VJ/W May 20, 1952l A. c. HOME-:YER 2,597,729

HEAT PUMP SYSTEM Filed July 1e, 1951 3 sheets-snee*b s 9 INVENTOR.

d j 4f/Wag c: Afa/75%@ BVMW@ Patented May 20, 1952 UNITED STATES PATENTOFFICE HEAT PUMP SYSTEM Arthur C. Homeyer, Essex Fells, N. J.

Application July 18, 1951, Serial No. 237,393

Claims.

rlhis invention relates to heat pumps and more particularly tomechanical and electrical devices for controlling the reversal of therefrigerant cycle in a heat pump.

Heat pump systems of the general type, above referred to, generallycomprise an outdoor heat transfer unit, an indoor heat transfer unitconnected by a piping system and control valves with a compressor whichforces a suitable refrigerant, such as methyl chloride or one of therefrigerante known as Freons, through the system. When the systemoperates in a cooling cycle the refrigerant is directed in gaseous formby the compressor first to the outdoor transfer unit, now operating as aheat dissipator or condenser, in which the refri-g erant is liquefiedand then through expansion valve means to the indoor transfer unit, nowoperating as a heat evaporator or absorber. In this latter unit the heatis absorbed and the refrigerant is again vaporized and flows back to thecompressor. When the system operates in a heating cycle the flowdirection of the refrigerant is reversed. As a result the compressordischarge of the refrigerant is rst directed to the indoor transfer unitwhich now becomes a condenser or heat dissipator.

The direction of ilow of the refrigerant from the discharge side of thecompressor to the suc tion side is controlled in heat pump systems asherein referred to, by so-called switch-over or change-over valves whichin turn are controlled manually or by temperature sensitive means suchas a thermostat.

As will be apparent, pressure differentials are developed between thecompressor discharge and suction sides during each operating cycle. Theymay be quite substantial and can readily reach approximately ZO poundsper square inch. As a result, an automatic shifting of the changeeovervalves from one postion into the other is dimcult under theaforementioned pressure conditions ben cause the magnitude of thenecessary port areas of the valves requires relatively large operatingforces and offers considerable technical problems. When the compressorstops, these pressure differentials eventually equalize in a timeinterval, sometimes quite appreciable and depending upon the ambienttemperatures.

There are known change-over valve designs employing power pistons, powerdiaphragms or motor operated constructions. However, the difculty withthe designs, as hitherto known, is that they are expensive and/or notreliable in operation. These aforementioned and related problems are soreal that such heat pump systems are 2 often equipped with manuallyoperated changeover valves which must be operated by hand for eachchange from a heating cycle to a cooling cycle and vice versa.

One of the principal objects of the present invention is to providecontrol means which permit a completely automatic control of a heat pumpsystem of the general type above referred to and a change of the systemfrom one cycle to the other at will or in response to automatictemperature sensitive devices demanding such change.

Another object of the inventionis to provide change-over valves whichare relatively inexpensive, employ features commonly used and reliablein operation, remain in the existing valve position at the end of anycycle pending a repeat of the same cycle, and insure positivechange-over when required.

Another object of the invention is to provide novel and improvedchange-over valves which are actuated by electromagnetic means includingsolenoids.

Another object of the invention, allied with the preceding one, is toprovide pressure sensitive means which control the valve solenoids andthe start of the compressor motor so that the sole noids are energizedonly when the pressure differential Within the heat pump system hasdropped below a predetermined low value. This has the advantage thatcomparatively small and low power solenoids can be employed to shift thevalves and also that compressor motors with low starting torque can beused since due to the pressure reduction at the end of each cycle thecompressor starts the next cycle against a low pres sure or even atequalized pressure in the system.

Another more specific object of the invention,

related to the preceding one, is to providepressure sensitive meanswhich are controlled by the pressure differential between the dischargeside and the suction side of the compressor and which control theopening and closing of the energizing circuits of the valve solenoids.

Another object of the invention is to provide pressure equalizing meanswhich serve to adjustably accelerate the decrease of the pressuredifferential at the end of each cycle. This has the advantage ofshortening the oif period between two cycles and thereby permitting therapid initiation of a new cycle which may either be the same cycle or areverse cycle.

Other and further features, objects, and advantages of the inventionwill be pointed out 3 hereinafter and set forth in the appended claimsforming part of the application.

In the accompanying drawing several now preferred embodiments of theinvention are shown by way of illustration and not by way of limitation.

Fig. l is a diagrammatic view of a reversible refrigeration systemcommonly known as a heat pump.

Fig. 2 is a typical circuit diagram for operating a heat pump accordingto Fig. 1.

Fig. 3 is a detail view of one of the components of the heat pumpinstallation on an enlarged scale.

Fig. 4 is a sectional view of a modification of the component accordingto Fig. 3, and

Fig. 5 is a detail View of a form of control member for use in a heatpump control system of the type illustrated in Fig. 1.

Referring first to Fig. 1 in detail, the heat pump installationaccording to this gure comprises two heat exchangers I and 2 which areconnected by suitable pipings to the suction and compression side,respectively, of a compressor 3. The compressor serves to pump asuitable refrigerant through the piping system and the heat exchangers.Heat exchanger may be visualized as an outdoor heat transfer unit andheat exchanger 2 as an indoor heat transfer unit.

Each heat exchanger acts either as evaporator for liquefied refrigerantor as condenser for vaporized refrigerant depending upon whether theinstallation is operated to heat or cool a conditioned space. Theinstallation further comprises two so-called change-over, reversing or Mswitch-over valves, generally designated by 4 and 5 respectively. Thesevalves serve to control the direction of ow of the refrigerant throughthe system. In addition, the system is equipped with conventionalexpansion valves 6 and 1 respectively, sensing elements 8 and 9 ofthermostats controlling the expansion valves, a receiver I0, and allother valves and devices customarily used in connection withinstallations of the general type here referred to.

The functioning of the installation as a heating or cooling system isdetermined by the setting of a room thermostat as will be more fullyexplained in connection with Fig. 2.

As was previously explained, the pressure diff ferentials developedwithin an installation of the type here referred to are substantialduring the operating cycle. It was further previously mentioned that asa result of these comparatively high differential pressures theoperation of the change-over valves 4 and 5 offers considerabledifficulties. According to the invention, these difficulties areeliminated or at least considerably reduced by providing a differentialpressure switch generally designated by |I. As will be more fullyexplained hereinafter, this switch controls the operation of thechange-over valves so that these valves will be moved from one positioninto the other only when the differential pressure is reduced to amagnitude which can be conveniently overcome by change-over valveactuators of comparatively small size and relatively low power. SwitchII may be so adjusted that the change-over valves become operative onlywhen the pressure within the system is approximately equalized or atleast reduced to a predetermined low value.

Practical experience shows that under certain operating conditions anexcessively long period of time elapses before the pressure differentialdisappears or reaches the aforementioned low value and switch canoperate. To expedite the operation of switch and hence the operation ofthe change-over valves 4 and 5, an equalizing valve, adjustable as toport or orice opening, generally designated by I2, may be provided. Aswill be noted, differential pressure switch I I and equalizing valve I2are connected between a pipe I3 communicating with the pressure side ofcompressor 3 and a pipe I4 leading to the suction side of thecompressor. The installation according to Fig. l is shown set forheating. Accordingly, the hot gas discharge of compressor 3 is directedthrough pipe |3, change-over valve 5 and a pipe I5 to the indoor heatexchanger 2 which now dissipates heat and acts as a condenser. Theliquefied refrigerant then flows through a pipe I6, a now open valve I1,receiver IIJ, a pipe I8, expansion valve 6, the outdoor heat exchanger Iin which the liquefied refrigerant is again evaporated, a pipe |9,change-over valve 4, and pipe I4 back to the suction side of thecompressor.

When the installation is set for cooling, heat exchanger I operates ascondenser and heat exchanger 2 as evaporator.

The hereinbefore described function of the installation is conventional.It is therefore believed that a more detailed description is notessential for the understanding of the invention.

Change-over valves 4 and 5 are solenoid operated valves the solenoids ofwhich can be of comparatively small size since, as previously explained,the valves become operative only when the pressure differential withinthe system has completely or nearly disappeared. Equalizing valve I2,being of relatively small orifice size, is also solenoid operated and isconventionally used for this type of service.

The energizing circuits of the various valve solenoids will now beexplained in connection with Fig. 2. This figure shows the valvecircuits in detail. The circuit diagram further shows a defrost relaygenerally designated by 20 which is controlled by the icing conditionsat the heat exchanger coil of one of the heat exchangers.

As can be seen on Figs. l and 2, each changeover valve has two solenoidcoils c and h, each coil c serving to place the respective changeovervalve in a position for a cooling cycle and each coil h serving to placethe respective valve in a position for a heating cycle. The coils c arecontrolled by a relay C and the coils h by a relay H. The relay C isprovided with six pairs of contacts 25, 26, 21, 28, 29, and 30, whichare controlled by six contact arms. The relay contacts and the said armsare so arranged that contacts 25, 26, and 21 are closed, and contacts28, 29, and 30 are open when the relay is deenergized, and that contacts28, 29, and 30 close just before contacts 25, 26, and 21 open when therelay is energized. Similarly, relay H is shown as being equipped withsix pairs of contacts 3|, 32, 33, 34, 35, and 36, of which contacts 3|,32, and 33 are closed, and contacts 34, 35, and 36 are open when relay His deenergized. The opening of contacts 3|, 32, and 33 occurs slightlyafter cont-acts 34, 35, and 36 are closed.

Relay 20 is equipped with three sets of contacts 31, 38, and 39, ofwhich contacts 31 and 39 are open and contact 38 is closed when relay 20is deenergized. Contacts 31 are in the energizing circuit of relay C,contacts 38 are in the energizing circuit of relay H, and contacts 39are connected in series with contacts 25 and 3|.

i"lhe entire control system is supplied with current from power linesthrough a transformer 4I. compressor motor 3 being connected directly bya switch 42 to the power lines. The switch is controlled by a magnetcoil 43.

The control system further comprises a room thermostat 44 ofconventional design, the movable contact of which can make contact witheither one of two stationary contacts to close a heating or a coolingcircuit, as will be more fully explained hereinafter.

The differential pressure switch Il, as shown in Figs. l, 2, and 3,comprises a pivotal contact arm which may be pivoted to a frame 5I as isshown in Fig. 2. Contact arm 50 has thereon a contact 52 coactingaccording to Fig. 2 with a pair of contacts 53 and according to Figs. 1and 3 with a contact 54. According to Figs. 2 and 3, arm 50 is pivotedbetween two bellows 55 and 56, bellows 56 communicating with thepressure side of the compressor through pipe I3 and bellows 55 with thesuction side through pipe I4. As will be apparent, the position of arm50 is controlled by the differential pressure conditions affecting thetwo bellows. The arrangement is so that contacts 52, 54 and 52, 53,respectively, are closed when the pressure differences in the entiresystem are approximately equalized or within the limits at which thechange-over valves 4 and 5 have been designed to operate.

The operational pressure of switch II may be conveniently adjusted bymeans of a spring 51, the tension of which can be adjusted by a setscrew 58.

Fig. 4 shows a modification of the differential cates with the pressureside of the compressor and the other with the suction side so thatdiaphragm is deflected according to the pressure difference on oppositesides of the diaphragm. Diaphragm 60 supports a post 62 to which islinked a bar 63. This bar guided through an elongated opening 64 ofhousing 6I by means of a bellows 65 so that bar 63 can pivot to acertain extent about its connection at bellows 65 in response to adeflection of diaphragm 60. Bar 63 coacts with a contact arm 66 pivotalabout a pivot 61. Arm 66 supports contact 52 which is biased towardengagement with contact 54 by a loaded spring 68. The arrangement isagain so that contacts 52 and 54 are closed when the pressure on bothsides of the diaphragm is equalized or within the aforementioned limits.

The equalizing valve I2 is of conventional design. It is connectedsimilarly to switch II between the pressure and the suction side of thecompressor and serves to accelerate the drop of the pressure differencewithin the system at the end of a heating or cooling cycle so that thechange-over valves can operate under the control of switch I I. Valve I2is operated by means of a solenoid coil. The energizing circuit of valvecoil is controlled by the defrost relay 20.

The energizing circuit of the defrost relay 20 is controlled by the airflow through a duct 13 in which the windings of the coil of one of theheat exchangers I or 2, preferably exchanger I, are disposed. As aresult of the air flow across the coil, a certain pressure differencewill develop in the spaces on opposite sides of the coil, depending uponthe areas of the passageways between the.

windings of the coil. This pressure difference is used to control apressure sensitive device, gen-i erally designated by 1I, which in turncontrols the defrost relay 20. The device is shown as comprising acasing including two chambers 15 and 15' separated by a diaphragm 16.The space 18 on one side of the coil communicates through a pipe 14 withspace 15 and the space 18 on the opposite side of the coil communicatesthrough a pipe 'I9 with the space 'I5'. A contact 11 engageable withcontacts -IIl abuts against diaphragm 'I6 and is so arranged thatcontacts 10 and 11 are disengaged when the windings of the coil of theheat exchanger are not or only comparatively slightly coated with ice.When the coil windings become more and more heavily coated with ice thepassageways between the coil windings are correspondingly decreased. Asa result, the pressures within the spaces 'I8 and 15 increase, and thepressures within the spaces 18 and 'I5' decrease, resulting in adeflection of diaphragm 16 into the space 15 until finally contacts 10and 11 engage each other, thereby energizing relay 20.

It will be evident that instead of sensing the icing conditions at theheat exchanger by the areas of the said passageways, other suitablesensing means may be employed; for instance, a feeler may be providedwhich probes the thickness of the ice coating. It is also sometimespractical and advisable to provide a timing device which closes contacts10 and 11 at selected intervals for a predetermined period of time.

The system, as hereinbefore described, operates as follows:

Let it be assumed that for the purpose of initiating a cooling cycle themovable contact arm of thermostat 44 engages the cooling contact(righthand contact), then an energizing circuit is closed for relay Cfrom a supply lead through a lead 8|, the coil of relay C, a lead 82,contacts 32, a lead 83, contacts 21, a lead 84, contacts 53, 52, a lead85, and back to a supply lead 8B. As a result, relay C closes contacts28, 29 and 30 and opens contacts 25, 26 and 21 after closing theaforementioned contacts. The closing of contacts 29 establishes aholding circuit from supply line 88 through the respective contact ofthermostat 44, lead 8|, the coil of relay C, contacts 32, lead 83,contacts 29, and back through lead B5 to supply line 86. The closing ofcontacts 28 coinpletes a circuit for the coil 43 of switch 42 from thesupply line Si), the switch coil 43, a lead 81, contacts 28 and backthrough lead 85 to supply line 86. As a result, switch 42 closes andconnects the motor of compressor 3 to the power lines 4I) so that thecompressor becomes operative. Simultaneously, contacts 30 closeenergizing circuits for the cooling coils c of the changeover valves 4and 5. These circuits extend from supply line 8D through a lead 88, coilc of valve 5, a lead 89, contacts 36, lead 84, back to supply line 86 aspreviously described. Coil c of change-over valve 4 is connected inparallel to coil c of valve 5 by leads 9D and 9i. As a result, coils cof the change-over valves move the same from the heating positions shownin Fig. 1 to the cooling positions. As to the various conventionalvalves shown in the piping system of Fig. l, it is assumed that the saidvalves are placed in the proper positions by conventional means, adetailed description of which does not appear to be essential to theunderstanding of the invention.

During the hereinbefore described cycle, a considerable pressuredifference will be developed between the pressure side and the suctionside of 7 the compressor. As a result, one of the bellows of switch Hwill be expanded and the other be compressed so that contacts 52, 53 aredisengaged. Consequently, the circuit of coils c is interrupted atcontacts 53 but the energizing circuit of the relay C remains closed byreason of the previous- 1y described holding circuit over the contacts29.

Let is now be assumed that all the components of the circuit system arein the position shown in Fig. 2 and that thermostat 44 engages itsheating contact, thereby initiating a heating circuit. As a result, thecoil of relay H is now energized from power supply line 80, therespective contact of thermostat 44, a lead 95, the coil of relay H,contacts 38, a lead 96, contacts 26, a lead 91, contact 33, a lead 98,and through contacts 53 and 52, and lead 85, back to supply line 86.Consequently, relay H attracts its contact arms setting up circuits formotor switch 42 and heating coils h of the change-over valves 4 and 5,which circuits can be conveniently traced from the previous description.Contacts 53 will again be opened when compressor 3 starts due to thepressure differentials developed during the heating cycle.

As will appear from the previous description, neither a cooling cycle ora heating cycle can be initiated by thermostat 44 unless contacts 52 ofswitch Il close contacts 53. In other words, a change-over from onecycle to the other is not possible as long as there is a pressuredifferential in the system higher than the one for which thedifferential pressure switch Il is adjusted. It will be obvious thatimmedaitely following the completion of either running cycle, theinternal pressures of the system tend to equalize. It will now beapparent that for a certain period of time neither a heating cycle nor acooling cycle is in operation. If this off cycle is of sumcientduration, the internal pressure of the system eventually reachesapproximate equalization, contacts 53 close and a new cycle begins whenthe thermostat demands it.

As previously described, this arrangement has the advantage that thesolenoids of the changeover valves do not have to overcome anysubstantial pressure and can, hence, be of comparatively small size andpower. Furthermore, the solenoids of the change-over valves can bedesigned or intermittent duty.

Let it now be assumed that the system is operating in a heating cycle,that is, the contact arm of thermostat 44 engages the heating contactand relay H is energized as previously described. Let it further beassumed that the icing condition at the respective heat exchanger coilis such that contact 11 closes contacts 1D as described in connectionwith Fig. 5. As a result, an energizing circuit is closed for the coilof relay 2G which can be traced from supply line 80 through a lead IGC,the coil of relay 2U, a lead IUI, contacts 1B and 11, lead 85, back tosupply line 86. As a result, relay 2D closes its contacts 31 and 39 andopens its contacts 38. The opening of contacts 38 interrupts theenergizing circuit of relay H which becomes deenergized and returns itscontact arms into the position shown in Fig. 2. The closing of contacts38 of relay 20 and 3l of relay H establishes an energizing circuit forthe coil of equalizing valve l2. This valve, as previously explained,serves to equalize more rapidly the pressure differences in the systemso that the differential pressure switch l l ca-n close contacts 53. Theclosing of contacts 31 of relay 2U establishes an energizing circuit forthe coil of relay C. This circuit is independent f 8 of thermostat 44and may be traced from supply line through lead |00, contacts 31, coilof relay C, lead B2, contacts 32 now closed, lead 83, contacts 21, lead84, contacts 53 now closed, andlead 85, back to supply lead 86.Consequently, relay C reverses the flow direction of the refrigerant, aspreviously described, so that the heavy ice formations on the respectiveheat exchanger coil are removed or at least reduced, contacts 10 areopened again, relay 20 becomes deenergized and the entire system againfunctions under the control of thermostat 44.

While the invention has been described in detail with respect to certainnow preferred eX- amples and embodiments of the invention it will beunderstood by those skilled in the art after understanding theinvention, that various changes and modifications may be made withoutdeparting from the spirit and scope of the invention, and it isintended, therefore, to cover all such changes and modifications in theappended claims.

What is claimed as new and desired to be secured by Letters Patent is:

l. A heat pump of the type including compressor means, a pair of heatexchanger means, and change-over valve means connected by piping meansin a reversible refrigerant cycle system, in combination withelectromagnetic means associated with said change-over valves forshifting the same from the heating cycle position into the cooling cycleposition and Vice Versa in response to an energization of theelectromagnetic means, pressure sensitive means connected with thepiping means and responsive to internal pressure differentials in thesystem, and switch means controlled by said pressure sensitive means andconnected in circuit with said electromagnetic means for controlling theenergization thereof, the said pressure sensitive means being arrangedto set the switch means for energization of the electromagnetic meansonly when the said pressure differentials within the piping means arebelow a predetermined value.

2. A heat pump as defined in claim l, wherein said pressure sensitivemeans communicate with the pressure side and the suction side of thecompressor means, and wherein said switch means controlled by thepressure sensitive means are included in an energizing circuit with saidelectromagentic means, the said pressure sensitive means being set andarranged to actuate said switch means in response to a pressuredifference between the pressure side and the suction side of thecompressor means below said predetermined value.

3. In a heat pump, in combination electrically controlled compressormeans, a pair of heat exchanger means, change-over valves includingsolenoids for shifting the valve means from one position into the otherby energization of the respective solenoids, piping means connecting theaforesaid components of the pump in a reversible refrigerant cyclesystem, thermostat means including control contacts for initiating acooling or a heating cycle, first relay means controlling the solenoidsof the change-over valve means for shifting the latter into the positionfor a heating cycle and controlling the actuation of the compressormeans, second relay means controlling the solenoids of the change-overvalve means for shifting the latter into the position for a coolingcycle and controlling the actuation of the cornpressor means, circuitmeans connecting said thermostat contacts and said relay means in anenergizing circuit for energizing the respective relay means in responseto the closing of the respective thermostat contact, and pressuresensitive means responsive to pressure differentials in said pipingmeans and comprising switch contacts included in said circuit means,said pressure sensitive means being arranged to actuate their switchcontacts only when the pressure dinerenu tials within the piping meansare bel-ow a predetermined value.

4. A heat pump as dened in claim 3, wherein each of said relay meanscontrols a holding circuit for its coil by-passng said switch contactsof the pressure sensitive means, each of said holding circuits beingclosed upon energization of the respective relay means.

5. A heat pump as defined in claim 1, in combination with equalizingvalve means included in said piping means between the pressure side andthe suction side of the compressor means and arranged to accelerate thedrop of the pressure diierential in the piping means at the end of eachcycle, and electro-mechanical actuating means controlled by theoperational condition at one of the heat exchanger means at the end ofeach cycle and controlling the operation of said equaliaing valve means.

6. A heat pump as defined in claim 5, wherein said electro-mechanicalactuating means comprise sensing means sensing the icing conditions atone of the heat exchangers, switch means controlled by the sensing meansin accordance with the said icing conditions, and relay means controlledby the switch means of the sensing means and controllingr the aforesaidcircuit means so as to cause, when actuated, the respective one of therelay means included in the said circuit to shift the change-over valvemeans into the position for a heating cycle.

7. A heat pump as defined in claim 6, wherein one of said heatexchangers is disposed within a duct for passing a fluid across the saidheat exchanger, ancl wherein said sensing means comprises a closedhousing, a diaphragm means therein so as to form two chambers within thehousing, and conduit means connecting duct portions on opposite sides ofthe said heat exchanger with said chambers for varying the deflection ofthe diaphragm means by the pressure difference in said chambers ascaused by the flow of a fluid 10 through said duct and across the saidheat exchanger, said switch means of the sensing means being controlledby the deiiection of the diaphragm means.

8. A heat pump as defined in claim 7, wherein the said heat exchangerincludes heat dissipating components subject to the formation of icecoating thereon during operation, the passage areas between the saidcomponents, as determined by an ice coating, controlling the pressurediierence on opposite sides of the said heat exchanger.

9. A heat pump as dened in claim l, wherein pressure sensitive meansconnected with piping means comprise a movable member, conduit meanstransmitting the pressure at the discharge side of the compressor meansto one side or' the movable member, and conduit means transmitting thepressure at the suction side of the compressor means to the oppositeside of the movable member, the position of the said movable memberbeing controlled by the pressure difference between the two sides of thecompressor `means; and wherein said switch means comprise relativelymovable contact means, the relative position of the said contact meansbeing controlled by the position of said movable member so as to setsaid switch means for energization oi the electromagnetic means when themovable member is in a position corresponding to a pressure differentialbelow said predetermined value.

1Q. A heat pump as defined in claim 9, wherein the said pressuresensitive means comprise two bellows, one communicating with thepressure side or the compressor means and the other with the suctionside, each of said bellows being in operative engagement with saidmovable member, the position of the said member being controlled by therelative expansion and contraction of said bellows.

ARTHUR C. HOMEYER.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,446,910 Dickens Aug. 10, 19482,513,373 Sporn July 4, 1950 2,558,933 Dillman July 3, 1951

